The present invention relates to a new lighting head assembly for use in lighting devices such as commercial and residential lighting fixtures, flashlights and miniature flashlights. More particularly, the present invention relates to compact and efficient lighting head assemblies for use with lighting devices of the type employing a high brightness light emitting diode (LED) to provide a smooth uniform spotlight beam having sharp edges.
Most commercially available lighting devices are designed to provide an on-axis, high intensity peak in their beam distribution as is typically found in flashlights with smooth reflectors or specialty architectural spotlights such as picture lights. In other words, most conventional lighting assemblies provide a central spot that is highly illuminated with a surrounding beam fall off region that varies from assembly to assembly. In general, these smooth reflector type assemblies simply re-image the light source into the far field of the device and create a poorly distributed, non-uniform illuminated field. Attempts to provide a more uniform beam distribution include the use of multi-faceted reflectors, however, the resulting beam pattern tends to be Gaussian with no sharp edge definition between the area illuminated by the beam and the surrounding non-illuminated area. In both the faceted and smooth reflector cases, the reflector generally tends to be parabolic in shape. While this shape reduces the direct re-imaging of the light source, this solution simply smears the image taken from the far field of the light source and projects that smeared image in the far field of the flashlight beam thereby still providing a non-uniform light image in the far field of the lighting device.
Other prior art attempts to produce a focused light source include the provision of a standard convex lens with a relatively long convergence factor in front of an LED package. These devices also produce an unacceptable result as they capture the far field image from a plane projected in front of the LED package and simply enlarge the LED image and then reflects that image in a reversed pattern in the flashlight beam far field. If the beam pattern is carefully studied, an image of the emitter die, diode and reflector cup can easily be identified in the beam image.
In most of the prior art assemblies, in order to provide even the marginally acceptable results using the assemblies described above, the lighting device needed a large reflector and a relatively large lens with a long focal length. These components dictated that the head of the light assembly have a large dimension as well. Further, because the LED lighting elements generate a great deal of heat, a heat dissipation path must be provided as well. In general, this heat dissipation path is simply provided in the form of creating a large volume of air space around the LED. All of these factors combined in the prior art to prevent the design of a compact lighting assembly that could incorporate a single high brightness LED.
Finally, in order to manufacture a portable lighting assembly that is compact it is desirable to provide a lighting assembly that can be operated using a single conventional battery such as a conventional AA or AAA cell battery. However, in order for this type battery to activate the LED, step up circuitry must be provided to increase the 1.5 volt battery output to at least the threshold voltage required to illuminate the LED. The drawback is that this circuitry is extremely sensitive to reversed polarity. Therefore there is also a need for providing reliable polarity protection thereby preventing a user from accidentally activating the lighting assembly with a battery that has been installed in reverse orientation.
Therefore, there is a need for a lighting device that produces a smooth, evenly distributed beam of light. In addition, there is a need for a lighting device that provides a high intensity beam of light that has a homogeneous illumination pattern. There is also a need for a high intensity flashlight beam that provides a uniform field of illumination and that has a sharp edge between the illuminated field and the non-illuminated field. There is a further need for a lighting head assembly that is compact and efficient in size while providing an integrated heat dissipation pathway. There is yet a further need for a compact lighting assembly that includes reliable and integrated polarity protection for the control circuitry therein.